Science Vocab chapter 4

2. system matter can enter from or escape to the surroundings.
5. substances that undergo the chemical changes.
9. the amount of a substance in a given volume.
10. of conservation of mass states that during a chemical reaction matter is not created or destroyed.
11. the new substances that form.
12. in chemistry when two or more elements or compounds combine to make a more complex substance, the reaction is classified as...
13. increases the reaction rate by lowering the activation energy needed.
15. when one element replaces another element in a compound, or if two elements in different compounds trade places, the reaction is a replacement.
17. a number placed in front of a chemical formula in an equation.
18. reaction the energy released as the products form is greater than the energy required to break the bonds of the reactants.

1. A material used to decrease the rate of a chemical reaction is an...
3. change any change that alters the form or appearance of a substance but does not change it into another substance.
4. the cells in your body contain thousands of biological catalysts called...
6. reaction more energy is required to break the bonds of the reactants than is released by the formation of the products.
7. occurs when compounds break down into simpler products.
8. a solid that forms from liquids during a chemical reaction.
9. system matter does not enter or leave
14. energy the minimum amount of energy needed to start a chemical reaction.
16. change A change in matter that produces one or more new substances.